Getting ready for some fan measurements using my propellor-comparison method of achieving equal (but unknown) airflows on two fans, and then measuring the noise level up close (*real* close) on both fans. This should provide noise/airflow figures of merit for each fan.

I have a sample or samples of five of the 120mm fans SPCR has reviewed, four from roundup 4 and one from roundup 2.

120mm fans that I own sample(s) of: their RPMs at 25CFM as measured by SPCR , my dBA measurement at that RPM and 0.25" from the center of the fan's hub, SPCR's dBA measurement at 1 meter, from SPCR Fan Roundup 2 or 4 (*n), and the fan identification:

SPCR measured a high 28dBA noise level on the UC12EB, noting a single tone noise. My UC12EBs (two of them) were purchased when the fan was first introduced and don't have that single tone noise. SPCR got 25CFM from the SFlexE at *what* RPM

To these 5 fans, I'll add the Scythe SlipStream 800 and do some one-on-one airflow comparisons, noting the noise level at 0.25" from the hub on each. This should be interesting!-------------------------------

As I proofed the above words, the parts arrived. The $17 tachometer works, but in the interests of haste, I didn't use it for these first measurements. I'm gonna have to move the sensor propellor back - it tried to sync on the GW NCB RPM (but not other fans).

These measurements were made quickly but not carelessly. I've taken pics of the fixture, and will add them later as an edit. Here's the results I got for 4 fans:

As my standard fan I selected the GW NCB fan, at 970RPM. SPCR sez that's what it takes to get 25CFM. I measured 971RPM on the propellor - as I said, it was trying hard to sync (probably same pitch).

My comments: aside from the 9-blade, the other 3 fan blades (by visual inspection) seemed to have very similar pitches. The SFlexE pitch was higher *near the hub*, but not at the edges of the fan, which is probably why its RPM is lower than the other two 7-blade fans.

How in the world SPCR got 25CFM out of the SFlexE at 590RPM I dunno. Either SPCR or I made a huge mistake. As I understand it, the only way for a 120mm fan to have that RPM advantage over another 120 is by having a drastically higher pitch... which the 9-blade fan does have and the SFlexE does not. Even the 9-blade needed almost another 100RPM beyond "590" to get the same sensor prop rotation rate.

Based on the highest RPM, the GW NCB fan has the highest measured noise and, presumably, the lowest pitch of these fans. I've always believed (and in one case, measured) that lower-pitch fans have an advantage in a typical PC case. My high regard for the NCB has always been for its performance in my cases.

Thus the caution: these are open-air measurements!

SPCR's fan noise measurements are very close to their room ambient noise, and perhaps below that for a fan or two. So differences of a couple-dBA get masked by the high ambient. I "close-miked" to avoid the room ambient problem. I had to block the sensor prop when making noise measurements; it was slightly unbalanced.

edit: added the following:

This fixture is made of white styrene .06" sheet. Note the small angle-brackets that locate all 25mm fans in the same spot, also styrene:

The $17 tachometer was not in use for these tests; I used my Extech stroboscope in the interests of getting done quickly. The fan is mounted on a 3/16" rubber strip and the entire fixture is supported by 9ea 3/8" square by 1/4" high "feet" made of very soft polyeurethane foam weatherstripping.

I've provided some noise measurements, all made under constant airflow (CFM) conditions in free air. [Fan measurements made in expensive acoustic testing facilities are also all made in free air.]

The simplest bottom line is, at constant airflow the fan with the lowest noise level wins. Alas, things aren't simple. For example, I did not report on the noise level of all SFlexE's, just on the one sample I have in hand. [Just as SPCR reported the noise level of the Enermax UC12EB fan(s) it had on hand.] But it's impossible for anyone to predict what the noise level will be of a specific fan you will buy tomorrow.

Also, most computer users do not actually use fans in free air. They mount them in computer cases most of the time. If the airflow in the computer case is restricted, this can impinge on the ability of the fan to perform its task. It's impossible for anyone to predict what fan A will do in case B using heatsink C on CPU D, which you may be overclocking...

I've provided some basic CFM/noise fan data. It requires some knowledge and experience to interpret. You can't download knowledge and experience off the internet. Alas, I can't provide it for you in a paragraph or two.

I've provided some noise measurements, all made under constant airflow (CFM) conditions in free air. [Fan measurements made in expensive acoustic testing facilities are also all made in free air.]

The simplest bottom line is, at constant airflow the fan with the lowest noise level wins. Alas, things aren't simple. For example, I did not report on the noise level of all SFlexE's, just on the one sample I have in hand. [Just as SPCR reported the noise level of the Enermax UC12EB fan(s) it had on hand.] But it's impossible for anyone to predict what the noise level will be of a specific fan you will buy tomorrow.

Also, most computer users do not actually use fans in free air. They mount them in computer cases most of the time. If the airflow in the computer case is restricted, this can impinge on the ability of the fan to perform its task. It's impossible for anyone to predict what fan A will do in case B using heatsink C on CPU D, which you may be overclocking...

Understandable and fair enough.

Quote:

I've provided some basic CFM/noise fan data. It requires some knowledge and experience to interpret. You can't download knowledge and experience off the internet. Alas, I can't provide it for you in a paragraph or two.

I disagree.

Your job as a reviewer is to review and evaluate the fans in the most simplest terms. Think of it as a story or a lesson - you're the teacher, we (the audience) are the kids. You have to assume that we know absolutely nothing about fans (or very little) so your main job is to educate us more about the fans to aid us in our purchasing decisions.

To merely throw all the data on the table and leave it open for interpretation is not the best idea. Anyone can come in here, pick up any of the four fans you tested, and leave thinking they made a good decision, when in reality it wasn't the best decision. I'm not knocking on you and I appreciate the work and effort you've put into this project. I guess what I'm really trying to say is that you wrote the review - does it really hurt to add a paragraph or two, perhaps a summary or conclusion on which fan is the best?

from the info I gather, the Scythe SS blows the same amount of air at a lower RPM and lower sound. That must mean it's good.

yes, I would say that is a fair conclusion from the above data. however, there is a caveat in that these experiments are conducted in free air and I suspect the Scythe Slipstream may have poor static pressure ability (for example on a restrictive heatsink or case) due to the rotor design; if you look at the Ultra Kaze or the new Noctua designed for high static pressure, they look very different from the Slipstreams.

[I suspect the Scythe Slipstream may have poor static pressure ability (for example on a restrictive heatsink or case).

I share your concern, and have from the start. That's why I put together a system using two of the SS fans for cooling (as exhaust and PSU fan, with the PSU fan not controlled by the PSU). I could find no problem with that system either noisewise or coolingwise. In particular, there were none of the problems that have been widely reported with the Noctua fans.

I cannot say that the SS is a worldbeater in such duty; I don't have enough data. I'm just saying I tried it; it worked; and I could detect no problems.

Another SPCR user has posted that he's going to try an SS fan on his TR 120SE shelf HSF. We need more such experiments to be performed, and the results reported here. Lots of people seem to be waiting for someone else to take the leap over an $8 - $10 item! Where is the spirit of adventure?

A little. What you provided would be good feedback for someone writing reviews for a living, but he is merely sharing data that he has gathered and making it available for us to use as we please. Maybe the title led you to expect more, but "Your job as a reviewer" seems you are expecting a little much or a little harsh on a knowledgable hobbiest sharing information.

I revised the sensor propellor arrangement, and made provision not to measure double the true sensor RPM. These measurements of 120mm fans use the revised sensor and are arranged from lowest pitch to highest pitch.

My conclusions: the new Scythe SlipStream fans are the quietest in open air, and also the highest pitch (lowest RPM). The Enermax Enlobal fan (my sample) is second, and (to my surprise!) the SFlexE is third. My YL SM sample and the two PWM fans are the loudest (highly undesirable). In the past, I compared fans at the same RPM, which I now know is a mistake.

My long-time favorite fan, the GW NCB, is the quietest low-pitch (high RPM) of this bunch. A low-pitch fan should do well in a PC-case environment.

I have some of the 800RPM and 1200 RPM models here, and I will run some tests shortly. I did the old "put hand behind fan" test, and I am shocked at how much air these really move at such quiet noise levels. Can't wait to see performance on a Infinity or TR Ultra120Xtreme.

what do you mean by "sweet", exactly?GW NCB and UC12EB, from your subjective perspective, which sounds more pleasant?

On just about all fans, the bearing noise has a degree of "gritty" noise. Some more, some less. On the UC12EB, this is completely, or almost completely, absent. I have no idea if this has anything to do with the advertised "magnetic suspension" (or something like that).

The UC12EB is more pleasant-sounding than the GW NCB.

Warning: SPCR's UC12EB samples exhibit a single-tone noise that my two samples don't have. Not all of these fans are the same, it seems.

Airflow doesn't always tell the whole story. There's a dead spot in the middle where the hub is, most of the airflow comes from the fan's edges. The Scythe SlipStream has a small hub. If mounted on the Ninja, it delivers more air to the core of the heatsink where it is most effective. Thus more suitable for some applications regardless of total aitflow.

I've used the AF PWM and the Scythe equivalent. I even took one of each apart. The IC motor controller is identical, the fans sound identical, and their noise levels measure the same with an SLM. For this reason, I chose not to include the AF and Scythe PWM fans in the above test.

Another SPCR member has posted that both PWM fans are made in the same factory, which would help explain the similarity of the two fans, noisewise.

I have one, it looks similar to the Scythe S-Flex except it's 1,500 RPM, but it has connectors for daisy-chaining 3-pin or 4-pin PWM fans and the wires are sleeved, kind of neat. I haven't used it yet. Do you think it's the same fan as S-Flex except for the sticker?

Can you make a system that has a heatsink, let's say ninja or ultra 120 extreme, a power resistor attached to it's bottom and you control the voltage you send though, and then a temperature sensor also attached to the bottom.

Then you would decide the heating power and desired temperature, and try to achieve that with different fans, and see how loud they go?

That would give each fans true utility as a cpu fan. Maybe not as a case fan.

I probably could but I won't. I am not a public servant to spend hours toiling to perform your experiment. I don't know anybody else who will, either. The only person who is going to expend effort on your idea for an experiment is you.

_________________JFK: What do our opponents mean when they apply to us the label "Liberal?" If by "Liberal" they mean...someone who looks ahead, who welcomes new ideas without rigid reactions,who cares about the welfare of the people, who believes we can break through the stalemate and suspicions that grip us in our policies abroad...then I'm proud to say I'm a "Liberal."

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